Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The transcriptional regulation of the Escherichia coli trp-linked opp operon that encodes the oligopeptide permease was investigated by using lambda plac Mu51-generated lac operon fusions. Synthesis of beta-galactosidase by strains harboring oppA-lac, oppB-lac, and oppD-lac fusions occurred at a basal level when the fusion-containing strains were grown in minimal medium. The addition of L-leucine or L-alanine to exponentially growing, aerobic cultures or shifting the aerobic fusion-containing strains to anaerobic growth medium increased the synthesis of beta-galactosidase from all opp-lac fusions. When transcription of the opp operon was induced by L-leucine, the differential rate of beta-galactosidase synthesis from each opp-lac fusion increased 8- to 10-fold; this increased rate of lacZ expression from the opp-lac fusions resulted in a 5- to 6-fold increase in total beta-galactosidase activity after maximum expression was achieved. Importantly, when F'123 derivatives harboring independently isolated E. coli opp-lac operon fusions were introduced into E. coli and Salmonella typhimurium, the data clearly demonstrated that the E. coli opp operon was expressed identically and responded to the same transcriptional regulatory signals in both E. coli and S. typhimurium. A comparison of beta-galactosidase synthesis by E. coli strains harboring an opp-lac operon fusion and either an oppE+ locus or an oppE mutation demonstrated that the reduction in peptide transport produced by the oppE mutation does not result from a decrease in the level of opp operon transcription.
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PMID:opp-lac Operon fusions and transcriptional regulation of the Escherichia coli trp-linked oligopeptide permease. 308 Apr 4

The influence of two new 1-desoxynojirimycin derivatives, BAY m 1099 and BAY o 1248, on rat small intestinal disaccharidases (sucrase, maltase, isomaltase, glucoamylase, lactase, trehalase) and alkaline phosphatase activity has been investigated in vitro. Both compounds are very potent alpha-glucosidase inhibitors. Tested in the range of 0.1-5.0 micrograms/ml, inhibition is strongest on sucrase (up to 97.1%) and glucoamylase (up to 96.7%). BAY m 1099 also reduced (up to 56.4%) beta-galactosidase (lactase) activity. For both inhibitors a competitive type of sucrase inhibition was demonstrated (Lineweaver-Burk plot). Affinity versus sucrase was unusually tight. The Ki of BAY m 1099 versus sucrase amounted to 1.14 x 10(-7) M and of BAY o 1248 to 6.92 X 10(-8) M (Dixon plot). Both inhibitors did not impair active transport of L-leucine or methyl-alpha-D-glucoside into everted rings of rat jejunum in vitro.
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PMID:Effect of 1-desoxynojirimycin derivatives on small intestinal disaccharidase activities and on active transport in vitro. 403 92

Pseudorevertants able to use L-leucyl-L-leucyl-L-leucine as a leucine source have been isolated from a Salmonella typhimurium strain carrying stable (nonreverting) mutations in pepN, pepA, and pepB. These strains carry mutations at a locus pto (peptidase T overproducer) tightly linked to pepT that cause an elevated expression of the tripeptidase peptidase T. An F' episome carrying the pto and pepT loci has been constructed and used to show that the pto mutations are cis dominant. Expression of beta-galactosidase from a Mu d1(Apr lac) insertion in pepT is increased by pto mutations. The pto mutations, therefore, define a site affecting the transcription of pepT.
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PMID:Overproduction of Salmonella typhimurium peptidase T. 631 18

Escherichia coli shifted from external pH (pH(O)) 7.0 to pH(O) 8.5-9.5 rapidly becomes tolerant to pH(O) 10.0-11.5, induction of tolerance (alkali habituation) being dependent on periplasmic or external alkalinization with either NaOH or KOH. Induction needs protein synthesis and makes organisms resistant to DNA damage by alkali and better able to repair any damage that occurs. Induction of tolerance was reduced by glucose (not reversed by cAMP) and by amiloride, was dependent on DNA gyrase and was abolished by fur and himA lesions (the latter suggests IHF involvement). Tolerance induction was not prevented by L-leucine, FeCl3 or FeSO4 nor by hns or relA mutations. Habituation probably involves attachment of IHF upstream of the promoter leading to DNA bending which switches on transcription. Habituation is aberrant in nhaA mutants, so ability to resist alkali damage may only arise if NhaA is induced, with extrusion of Na+ by this antiporter during alkali challenge. In accord with one tolerance component involving NhaA induction, beta-galactosidase formation from nhaA-lacZ fusions at pH(O) 9.0 was inhibited by glucose and amiloride.
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PMID:Regulatory aspects of alkali tolerance induction in Escherichia coli. 869 68

The ilvBNC operon of Corynebacterium glutamicum encodes acetohydroxy acid synthase and isomero-reductase, which are key enzymes of L-isoleucine, L-valine and L-leucine syntheses. In this study we identified the transcript initiation site of ilvBNC operon 292 nucleotides in front of the first structural gene, and detected the formation of a short transcript from the leader region in addition to the full-length transcript of the operon. This identifies the control of ilvBNC transcription by an attenuation mechanism involving antitermination. Mutations in the leader region were made and their effect on the operon expression in ilvB'lacZ fusions was quantified. Although a presumed leader-peptide-coding region is only one nucleotide away from the transcript initiation site determined, there is clear evidence to support the formation of this leader peptide: (i) the substitution of initiation codon ATG of the peptide by AGG reduced lacZ expression of the appropriate fusion construct to 19%; (ii) the replacement of three subsequent Val codons by Ala codons resulted in the loss of Val-dependent expression; and (iii) a leader peptide LacZ fusion resulted in active beta-galactosidase. Based on these results, it is concluded that transcription of ilvBNC is controlled by a translational-coupled attenuation mechanism. The absence of a ribosome binding site for leader peptide formation means that additional mechanisms may contribute to the transcription control at the decoding initiation step in the leader peptide formation.
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PMID:Attenuation control of ilvBNC in Corynebacterium glutamicum: evidence of leader peptide formation without the presence of a ribosome binding site. 1623 99

To induce extracellular secretion of beta-galactosidase synthesised by Kluyveromyces fragilis 28, it was used glycine, L-asparagine, L-leucine, dimethyl fluoride, dimethyl sulfoxide, cetyldimethylethylammonium bromide, penicillin G and glycolipids from Candida antarctica. The highest increase in the secretion of beta-galactosidase was obtained in the yeast culture cultivated in the medium with polypeptone when glycine was used as the secretion inductor. The extracellular activity of beta-galactosidase reached 0.416 A.U./ml, and was 10-fold higher than the beta-galactosidase activity reported in the control group.
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PMID:The effect of some conditions on the secretion of extracellular beta-galactosidase synthesised by Kluyveromyces fragilis 28. 2475 88